For example, in Japanese Unexamined Patent Application Publication No. 2004-1635, an example of a conventional passenger airbag device is disclosed. In this passenger airbag device, an airbag cover for covering a passenger airbag is provided with tear lines formed thereon for cleaving the airbag cover. At a vehicle collision, the airbag cover is cleaved along the tear lines and a development door is developed so as to allow the passenger airbag to inflate and develop outside the airbag cover.